Sophia University

About: Sophia University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Nonlinear system & Catalysis. The organization has 4986 authors who have published 7657 publications receiving 106567 citations. The organization is also known as: Jōchi Daigaku.

Photodegradation of tetrahalobisphenol-A (X = Cl, Br) flame retardants and delineation of factors affecting the process

Abstract: The photoassisted degradation (HPLC-UV absorption), dehalogenation (HPLC-IC) and mineralization (TOC decay) of the flame retardants tetrabromobisphenol-A (TBBPA) and tetrachlorobisphenol-A (TCBPA) were examined in UV-irradiated alkaline aqueous TiO2 dispersions (pH 12), and for comparison the parent bisphenol-A (BPA, an endocrine disruptor) in pH 4–12 aqueous media to assess which factor impact most on the photodegradative process. Complete degradation (2.7–2.8 × 10−2 min−1) and dehalogenation (1.8 × 10−2 min−1) of TBBPA and TCBPA occurred within 2 h of UV irradiation, whereas only 45–60% mineralization (2.3–2.7 × 10−3 min−1) was complete within 5 h for the flame retardants at pH 12 and ca. 80% for the parent BPA. Factors examined in the pH range 4–12 that impact the degradation of BPA were the point of zero charge of TiO2 particles (pHpzc; electrophoretic method), particle or aggregate sizes of TiO2 (light scattering), and the relative number of OH radicals (as DMPO– OH adducts; ESR spectroscopy) produced in the UV-irradiated dispersion. Dynamics of BPA degradation (2.0–2.4 × 10−2 min−1) were pH-independent and independent of particle/aggregate size, but did correlate with the number of OH radicals, at least at pHs 4 to 8–9, after which the rates decreased somewhat at pH > 9 with decreasing adsorption owing to Coulombic repulsive forces between the very negative TiO2 surface and the anionic forms of BPA (pKas ca. 9.6–11.3), even though the number of OH radicals continued to increase at the higher pHs.

The microwave-/photo-assisted degradation of bisphenol-A in aqueous TiO2 dispersions revisited Re-assessment of the microwave non-thermal effect

Abstract: The microwave-assisted photodegradation of bisphenol-A (BPA) in the presence of TiO2 was examined at ambient temperature to unravel some details on the importance of the microwave non-thermal effect. Normally, bisphenol-A photodegrades under microwave irradiation as a result of a thermal effect emanating from the microwave radiation which sees increase in temperature in the aqueous TiO2 dispersion. However, on cooling the dispersion with circulating silicone oil at −20 °C, the temperature of the dispersion could be maintained constant at 21 °C. Under the latter irradiation conditions, the microwave-assisted photodegradation of BPA was shown to be not only due to a microwave thermal effect, but also to a significant non-thermal effect that might implicate hot-spots on the TiO2 particle surface leading to enhanced photodegradation under constant ambient temperature. Other origins of the microwave non-thermal effect may include additional formation of charge carriers on the photomediator TiO2 and formation of additional trap sites that may otherwise prolong the lifetimes of the charge carriers through diminished recombination and ultimately increase process kinetics.

Relativistic Thermal Bremsstrahlung Gaunt Factor for the Intracluster Plasma. II. Analytic Fitting Formulae

Abstract: We present accurate analytic fitting formulae that summarize the results of the recent calculation by Nozawa, Itoh, & Kohyama on the relativistic thermal bremsstrahlung Gaunt factor for the intracluster plasma. The fitting is carried out for 1 ≤ Zj ≤ 28, 6.0 ≤ log T ≤ 8.5, -4.0 ≤ log(ω/kBT) ≤ 1.0 by combining the relativistic Gaunt factor with the nonrelativistic exact Gaunt factor smoothly, where Zj is the charge number of the ion, T is the temperature in kelvins, and ω is the angular frequency of the emitted photon. We also present an accurate analytic fitting formula for the nonrelativistic exact Gaunt factor. This fitting formula is best suited for relatively low-temperature plasmas in which the relativistic effect is negligible. The present analytic fitting formulae will be useful for the analysis of the X-ray emission which comes from the intracluster plasma as well as thef other X-ray sources.

Influence of the image charge effect on excitonic energy structure in organic-inorganic multiple quantum well crystals

Abstract: We have experimentally compared the excitonic properties of hybrid multiple quantum wells, (C${}_{\text{6}}$H${}_{\text{5}}$-C${}_{\text{2}}$H${}_{\text{4}}$NH${}_{\text{3}}$)${}_{\text{2}}$PbBr${}_{\text{4}}$ and (C${}_{\text{4}}$H${}_{\text{9}}$NH${}_{\text{3}}$)${}_{\text{2}}$PbBr${}_{\text{4}}$, using photoluminescence, reflection, and photoluminescence excitation measurements. We focused on the contribution of the image charge effect (ICE) to the excitonic energy structure in these materials which have different dielectric constants of the barrier layers. We have found that the binding energies of the $2s$ and $3s$ excitons are considerably enhanced by ICE, while the contribution of ICE to the $1s$ excitons is smaller because of the small Bohr radius, which is comparable to the well width.